The presently disclosed embodiments relate in general to an electrophotographic image forming apparatus and its subcomponents, and more particularly to an improved cleaning device that has excellent wear resistance and mechanical robustness and is used to remove or clean the residual toner and other debris from a charge retentive belt or drum surface of an image forming member.
In electrophotographic applications such as xerography, a charge retentive photoreceptor belt or drum is electrostatically charged according to the image to be produced. In a digital printer, an input device such as a raster output scanner controlled by an electronic subsystem can be adapted to receive signals from a computer and to transpose these signals into suitable signals so as to record an electrostatic latent image corresponding to the document to be reproduced on the photoreceptor. In a digital copier, an input device such as a raster input scanner controlled by an electronic subsystem can be adapted to provide an electrostatic latent image to the photoreceptor. In a light lens copier, the photoreceptor may be exposed to a pattern of light or obtained from the original image to be reproduced. In each case, the resulting pattern of charged and discharged areas on photoreceptor form an electrostatic charge pattern (an electrostatic latent image) conforming to the original image.
The electrostatic image on the photoreceptor may be developed by contacting it with a finely divided electrostatically attractable toner. The toner is held in position on the photoreceptor image areas by the electrostatic charge on the surface. Thus, a toner image is produced in conformity with a light image of the original beam reproduced. Once each toner image is transferred to a substrate, and the image affixed thereto form a permanent record of the image to be reproduced. In the case of multicolor copiers and printers, the complexity of the image transfer process is compounded, as four or more colors of toner may be transferred to each receiving substrate sheet or paper. Once the single or multicolored toner is applied to the substrate, it is permanently affixed to the substrate sheet by fusing so as to create the single or multicolor copy or print. Following the photoreceptor to the receiving substrate toner transfer process, it is necessary to at least periodically clean the charge retentive surface of the photoreceptor. In order to obtain the highest quality copy or print image, it is generally desirable to clean the photoreceptor each time toner is transferred to the substrate. In addition to the removing of excess residual toner, other particles such as paper fibers, toner additives and other impurities (hereinafter collectively referred to as “residue”) remaining on the charged surface of the photoreceptor should also be completely removed and cleaned as well prior to the next printing cycle to avoid debris intererence with the recording of next new latent image thereon.
Various methods and apparatus may be used for removing residual particles/debris from the imaging surface of the photoreceptor. For example, a cleaning brush, a cleaning web and a cleaning blade have been utilized; these devices are operated by wiping the imaging surface to effect cleaning. After prolonged service in the machine, however, these devices become contaminated with toner and debris and pre-maturely lose their cleaning efficiency which requires frequent costly replacement in the field. The shortcomings and pre-mature failure of these devices, made way for the development of another prevalent and improved form of cleaning known as elastomeric blade cleaning.
Elastomeric cleaning blades made of rubberlike material and brushes are employed to remove residue/debris from a photoreceptor surface. A typical elastomeric blade, made of inexpensive/low-cost crosslinked polyurethane, is used to scrape residue/debris from the photoreceptor surface. In operation, a rotating cleaning brush may first loosen, dislodge and abrade the unwanted toner and other residue from the photoreceptor surface prior to the subsequent sliding/wiping action of the elastomeric polyurethane blade to clean up the photoreceptor surface and be ready for next latent imaging formation process.
The currently used polyurethane blade in the electrophotographic cleaning process is an isotropic material having a Young's modulus that does satisfactorily meet both the lateral conformability requirement and resonant frequency requirement needed for effective cleaning performance. However, the currently used elastomeric polyurethane blade to clean the residue toners/debris from the surface of an organic photoreceptor belt or drum, has also been found to have certain deficiencies in blade cleaning process which are primarily a result of frictional sealing contact that must occur between the blade and the photoreceptor surface. Dynamic friction is the force that resists the relative motion between these two bodies that come into contact with each other as the photoreceptor is in cyclic motion against the stationary blade. This friction between the blade edge and the photoreceptor surface causes wearing away of the blade edge and damages the blade's intimate contact with the surface, resulting in material failure and eventual loss of the blade's cleaning efficiency. Therefore, a mechanically robust elastomeric polyurethane blade that has improved wear resistance is urgently needed to resolve the issue for functional life extension.
Various approaches have been employed to deal with problems associated with photoreceptor cleaning and oxidation in copying or printing machine environments, including the following disclosures: U.S. Pat. No. 5,208,639, U.S. Pat. No. 5,153,657, U.S. Pat. No. 5,138,395, U.S. Pat. No. 4,875,081, U.S. Pat. No. 4,864,331, U.S. Pat. No. 4,563,408, U.S. Pat. No. 4,264,191, and U.S. Pat. No. 5,208,639, the disclosures of which are hereby incorporated by reference in their entireties.
U.S. Pat. No. 5,208,639, hereby incorporated by reference in its entirety, discloses an apparatus for cleaning residual toner and debris from a moving charge retentive surface of an image forming apparatus. The present embodiment includes a multiple blade holder for selectively indexing each individual blade into position for cleaning the moving photoreceptor. The blade holder contains a number of cleaning blades mounted radially from a central core; by rotating the holder about its longitudinal axis a new cleaning blade is moved by the indexing device into the cleaning position to replace a failed blade. The indexing device removes the failed cleaning blade and positions a new cleaning blade in frictional contact with the photoreceptor for cleaning.
U.S. Pat. No. 5,208,639, hereby incorporated by reference in its entirety, discloses a cleaning blade which is made from a thermoplastic material having a compounded additive for lubrication. The cleaning blade is used in an electrophotographic printing machine to remove residual particles from a photoconductive surface. U.S. Pat. No. 5,153,657, hereby incorporated by reference in its entirety, discloses a blade member impregnated with inorganic particulates dispersed therein so as to reinforce the blade for improving blade life.
U.S. Pat. No. 4,875,081, hereby incorporated by reference in its entirety, discloses a blade member for cleaning a photoreceptor wherein an A.C. voltage is applied to the cleaning blade. Use of the A.C. voltage eliminates the need to bias the blade against the photoreceptor with a high frictional force and thus eliminates impaction of toner on the photoreceptor surface.
U.S. Pat. No. 4,864,331, hereby incorporated by reference in its entirety, discloses an offset electrostatic imaging process which includes the steps: (a) forming a latent electrostatic image on a dielectric imaging member, with the dielectric imaging member being prepared by coating an electrically conductive substrate with a porous layer of a non-photoconductive metal oxide using a deposition process; (b) developing the latent electrostatic image with a developer material which comprises a silicone polymer and from about 0.5 to about 5 percent by weight of a metal salt of a fatty acid; (c) transferring the developed image to an image receiving surface by applying pressure between the dielectric imaging member and the image receiving surface; (d) cleaning the dielectric imaging member using a first cleaning means which is effective to remove developer material residue from about the surface of the porous oxide layer; and (e) further cleaning the dielectric imaging member using a second cleaning means which is effective to remove developer material residue from the pores below the surface of the oxide layer.
U.S. Pat. No. 4,563,408, hereby incorporated by reference in its entirety, discloses an electrophotographic imaging member, which includes a conductive layer, a charge transport layer comprising an aromatic amine charge transport or hydrazone molecule in a continuous polymeric binder phase, and a contiguous charge generation layer comprising a photoconductive material, a polymeric binder and a hydroxyaromatic antioxidant. An electrophotographic imaging process using this member is also described.
U.S. Pat. No. 4,264,191, hereby incorporated by reference in its entirety, describes a laminated doctor blade for removing excess marking material or other material from a surface. The blade comprises a relatively hard layer of a smooth tough material and a relatively soft layer of resilient material.